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Re: empty test


From: Eric Blake
Subject: Re: empty test
Date: Sun, 09 Apr 2006 13:17:36 +0000

> > >   * lib/autotest/general.m4 (_AT_CHECK): Avoid syntax error on empty
> > >   check.
> > 
> > That looks fine; please install.  Thanks.
> 
> Erm, instead of the
>   :; $1
> 
> could we just have
>   m4_default([$1], [:])
> 
> please?  This avoids the size overhead incurred for the non-pathological
> case.

Except that with your idea, with AT_CHECK([ ]) (note the space), the m4_default
sees it as non-empty but shell syntax disagrees.  I went the course of
minimally invasive patch, by always ensuring valid syntax (assuming, of course,
that the shell snippet handed to AT_CHECK is also valid outside of a subshell),
rather than trying to play m4 games to guess when syntax is valid.  Of course,
how we handle something like AT_CHECK([;]) is up in the air, since by itself, 
";"
is not valid as a script outside of a subshell, nor would it be valid with 
either
of our proposals.

-- 
Eric Blake




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